Several million migrants from Tajikistan, Uzbekistan and Kyrgyzstan have come to Moscow in search of work, according to the Associated Press. Many have found jobs in construction or at the city's various markets, which sell everything from clothing to construction materials.

Emergency workers described the makeshift homes they found in the warehouse, with hard cots that were stacked on top of each other in rows of four and no direct access to the outside, reported Agence France-Presse. The workers "lived in a metal annex that was equipped with a space heater," an unnamed law enforcement official said.

"They slept in frighteningly tight conditions, on hard bunk cots that were then stacked on top of each other," he said to AFP.

Another official said the workers probably left the space heater on all night to stay warm, according to AFP. Overnight temperatures were below freezing and most of central Russia is currently under snow.

"This is turning into a tradition — people living in markets," said Russia's Emergencies Minister Sergei Shoigu. "Someone must have settled them there. This facility was completely unsuitable for housing. I ask the law enforcement official to look into this."